Heretofore, there has been no known device available which could indicate directly the efficiency of an external combustion, heat exchange process. Various types of temperature registering devices have been utilized to indicate the temperature of combusted gases which are being discharged into the ambient. But, there has been no known indicating device which gives direct readings of efficiency.
Additionally there has been no device available to indicate the expected operating efficiency of an external combustion process even with the combustion process not operating.
Further there has not been known a device which is to indicate changes in the combustion process efficiency for an external combustion apparatus.
One of the primary reasons that there has not been a device to indicate efficiency directly is that efficiency of a combustion apparatus requires an analysis of the exit gas constituents and exit gas temperature is also required. The measurement of exit gas temperature is most common and can be readily ascertained. To calculate efficiency also requires the measurement by means of a gas analyzer to determine the percentage within the exit gas of carbon dioxide, oxygen and carbon monoxide. These readings can be employed within a certain mathematical formula to calculate the efficiency of the boiler for that moment of time that the test was performed. Most operators of boilers are not able to calculate the efficiency for their boiler either due to not having the special equipment needed to perform the gas analysis or not having the skill in order to make the efficiency calculation.
A boiler operating at poor efficiency can use 25% more fuel than the same boiler operating at close to optimum efficiency. This increased use of fuel can prove to be quite costly within a very short period of time of operating the boiler.
Use of only a temperature gauge to give an indication of the operating efficiency of a boiler is an unsatisfactory determination of efficiency. Additionally the boiler is not observed constantly which means that at a point in time when the boiler is observed it may be operating at fair efficiency when sometime prior to the observation the boiler had been operating at poor efficiency. There should be some means to not only record efficiency at the present operating time of the boiler but also record the lowest operating efficiency of the boiler.